Vehicles can be used as a tool to carry people and cargoes to bring great convenience. However, the engine of a general vehicle usually burns gas or diesel fuel as a power source. The exhaust gas of the engine not only causes air pollution but also harm the human health, and carbon dioxide in the exhaust gas will bring the greenhouse effect to intensify global warming.
In recent years, electric vehicles are gradually popular because the environmental awareness is enhanced and the electric vehicles don't have the problem of exhaust gas and have excellent energy efficiency. However, the loads of the electric motor and the battery of the electric vehicle increase with the increase of the load weight of the electric vehicle. When the load weight of the electric vehicle reaches a predetermined value, the battery of the electric vehicle is liable to be damaged by overload.
Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.